Containers for liquids are periodically drained for a variety of reasons. If the container is generally air tight, provision should be made for allowing air to enter the container. The air displaces the liquid leaving the container and enables the liquid to more readily drain. Fuel filter/water separators used in vehicle fuel systems must periodically be drained to purge contaminants which accumulate therein. In many types of fuel filter/water separators, air must be introduced into the body of the unit before the contaminants may be drained.
To enable air tight fuel filter/water separators to be drained, several types of venting drain valves have been previously developed. These drain valves are generally mounted at or near the bottom of the container. The valves introduce air into the container through an inlet while allowing the fuel and/or contaminants to drain through a fuel outlet in the valve. In some designs such as the one shown in U.S. Pat. No. 4,724,074, the air inlet is located in close proximity to the fluid outlet of the valve. In such designs it is usually necessary to prime the fluid outlet of the valve in advance of the air vent being opened. Priming the fluid outlet creates a slight vacuum inside the unit. Thereafter when the air vent is opened only air will be drawn in through the vent. This avoids liquid flowing outward through the vent as well as air being drawn into the unit through the liquid outlet opening. Either of these conditions would impede draining of the unit.
Self venting drain valves previously known to Applicants have been constructed in two ways. The most common type of self venting drain valve uses a threaded knob which is accepted into the underside of a fluid container. The knob contains two internal passageways. From a closed position the knob is rotated several turns causing it to move outward due to the interaction of the threads. Eventually, a liquid passageway is opened through the knob to the interior of the container. The opening of the liquid passageway primes the outlet of the drain valve. Further rotation of the knob additional turns opens an air passageway which vents the container and enables air to displace the liquid which flows outward through the liquid outlet of the valve. This type of self-venting valve though generally satisfactory presents certain disadvantages. First it requires the use of mating threads on the knob and the container. It also requires two separate seals and sealing surfaces. These aspects add to manufacturing cost for the valve and each is a potential source for leakage or failure.
Another type of self-venting drain valve employs a threaded drain knob and a spring loaded vent. As the knob is turned several rotations, a fluid outlet is opened. Further outward movement of the knob opens a spring loaded vent allowing air to enter the interior of the container. This construction is shown in U.S. Pat. No. 4,855,041, which is owned by the assignee of the present invention. Again, this type of drain valve construction has the associated expense and potential problems of threaded pieces and multiple seals.
The types of self-venting drain valves mentioned above have an additional drawback in that the drain knob must be turned multiple turns to reach an open condition. This takes time. Also, the knobs typically have no stops to prevent them from being over tightened when closed, or from being loosened too far to a point where the knob disengages the threads and falls off the container. It is also difficult to connect a hose to a drain valve that must be turned several turns to the open condition. This makes it difficult to attach a permanent hose to the drain valve to carry away fluid discharged from the container.
Another type of self-venting drain valve is shown in U.S. Pat. No. 4,753,266. This drain valve includes a rotatable knob positioned at the bottom of a container. The extent to which the knob of this valve must be turned to reach the open condition is less than in some other valve types. This drain valve presents the drawback that it is a costly construction which requires structural components inside the container to insure that air enters the vent passage and that only liquid comes out of the liquid drain port. A further disadvantage associated with this valve, as well as other types known to Applicants, is that they extend substantially beyond the lower wall of the unit or container on which they are mounted. This increases the probability that the drain valve may be inadvertently bumped open or completely knocked off the unit.
In some applications, such as rectangular shaped vessels, it is desirable to locate the drain valve on a side wall of the unit rather than on the underside. Most conventional self venting drain valve constructions cannot be used to drain fluid through both a vertical wall or a horizontal wall of a unit without modification. This increases the number of items that must be manufactured.
Thus, there exists a need for a self venting drain valve that is simpler and less expensive to manufacture. There further exists a need for a valve that is lower in profile, opens quickly, can be installed without modification either on a vertical or a horizontal wall and which can be used with a permanently attached hose or other conduit.